High impedance cabling systems minimize power loss by increasing the voltage of signals for transmission over the cable and then reducing the voltage at the receiving end. This step-up/step-down process correspondingly reduces the current flowing through the cable and therefore the power loss in the cable. Such cabling is often installed into buildings for signal distribution over certain distances (for example, exceeding 50 feet). The maximum voltage used on the cable varies around the world according to regulations: in the USA, 70V is the maximum voltage that can be used without requiring conduit for the cable; in Europe, 100V maximum voltages are common. Cabling used for evacuation systems or installed in the plenum spaces of buildings is subject to a variety of regulations related to fire safety.
In conventional high impedance signal distribution systems such as 70/100V loudspeaker systems, the power is delivered to the speaker as an increased voltage version of the input signal. The power is delivered at an increased voltage minimizing losses in the cabling whilst signals are delivered via digital networking, avoiding many of the drawbacks present in existing systems whilst increasing the quality and flexibility of the signal distribution system.
A typical schematic of a high-impedance audio signal distribution system is shown in FIG. 1. A transformer 10 at the power-amplifier output steps up the voltage to approximately 70 volts at full power. The transformer 10 primary windings are coupled to a low impedance line 12, and the secondary windings are coupled to a high impedance speaker cable 14. Each speaker 16, 20, 24, 28 has an associated step-down transformer 18, 22, 26, 30 that matches the 70V high impedance line 14 to each speaker's impedance. The primary windings of the speaker transformers 18, 22, 26, 30 are connected in parallel to the transformer secondary windings in the power amplifier.
Power line communication or power line carrier (PLC) systems carry data on a conductor also used for electric power transmission. Electrical power is transmitted over high voltage transmission lines, distributed over medium voltage, and used inside buildings at lower voltages. Powerline communications can be applied at each stage. Most PLC technologies limit themselves to one set of wires (for example, premises wiring), but some can cross between two levels (for example, both the distribution network and premises wiring). Typically the transformer prevents the signal propagating beyond a single cable, which requires use of multiple technologies for larger networks.
The IEEE 1901 working group of the Institute of Electrical and Electronics Engineers develops standards for high-speed power line communications. This technology allows computer networks to send data over electrical power lines (contrasting with approaches such as power over Ethernet which send power over computer network wires).
HomePlug is the family name for various power line communications specifications that support networking over existing in-building electrical wiring. Several different, non-interoperable specifications exist under the HomePlug moniker, with each offering certain performance capabilities and variable compatibility with other HomePlug specifications. Some HomePlug specifications target broadband applications such as in-home distribution of low data rate IPTV, gaming, and Internet content, while others focus on low-power, low throughput, and extended operating temperatures for applications such as smart power meters and in-home communications between electric systems and appliances. HomePlug AV is reported to provide 20-30 Mbps in a typical home setting. IEEE 1901 claims to provide up to 500 Mbps, although this is a theoretical maximum speed.
Packet switched networking technologies are often used to transport media signals (e.g. audio, video, MIDI, or other signals). For example, the Audio Video Bridging (AVB) protocols may be used to transport media signals over an Ethernet network and the Real-Time Transport Protocol (RTP) standard developed by the IETF is widely used to transport multimedia signals over the Internet across many different types of link technology. A wide variety of digital and analogue media signals can be conditioned for transmission via a packet switched network.
Dante is a high performance, IP based media signal transport technology that employs a packet switched network. An exemplary Dante system is disclosed in U.S. Pat. No. 7,747,725 and U.S. Patent Application Publication No. 2010/0235486.
In addition to packet switched networks, simple networks can be constructed using point-to-point digital protocols such as AES3, S/PDIF, MADI, SDI, DVI, etc. A common scenario is a multi-drop cable carrying a common digital signal to many receivers. In many cases, these protocols are designed to operate over short distances with specific types of cables. Transmission over long distances or cable types not envisaged by the original protocol specifications may require signals to be conditioned appropriately for transmission over a high impedance cabling system. Signals are de-conditioned at the receivers and may additionally be boosted by devices connected to the cabling to further extend the distance served by the cabling.
There is a need for improved systems, devices and methods directed to networking and signal distribution over high impedance cabling. The present disclosure is directed to overcome and/or ameliorate at least one of the disadvantages of the prior art as will become apparent from the discussion herein.